Extension ladder rung lock

ABSTRACT

A retractable rung lock for an extension ladder in which a pivotal lock body is normally positioned to engage simultaneously adjacent rungs on relatively movable ladder sections. To permit selective extension and retraction of the ladder sections a camming latch is operatively engaged with the lock body. The latch is longitudinally and pivotally movable on a mounting bracket to effect retraction of the lock body during extension or retraction of the ladder sections. The latch member and lock body are normally spring urged to their respective extended positions.

United States Patent [72] Inventor [2]] Appl. No.

[22] Filed [45] Patented [73] Assignee Edward H. Le Blauc Redwood City,Calif. 879,035

Nov. 24, 1969 Feb. 23,1971

Larson Manufacturing, Inc. Santa Clara, Calif.

[54] EXTENSION LADDER RUNG LOCK 15 Claims, 9 Drawing Figs.

[52] U.S. Cl...

501 FieldofSearch.....................................:::::::

References Cited UNITED STATES PATENTS 1,045,165. 11/1912 Moulton3,502,l73 3/1970 Arnold 3,502,175 3/1970 Bullock PrimaryExaminer-Reinaldo P. Machado Attorney-Flehr, Hohbach, Test, Albritton &Herbert EXTENSION LADDER RUNG LOCK BACKGROUND OF THE INVENTION tion to aretracted position to permit selective extension or retraction of theladder sections relative to each other.

2. Description of the Prior Art Wooden and metal extension ladders havebeen used for many years and various lock mechanisms have been devisedfor retaining movable ladder sections in predetermined extendedpositions relative to each other. The lock mechanism of the presentinvention possesses the important safety feature of engaging alignedrungs of two ladder sections simultaneously to insure safe utilizationthereof and to preclude accidental release of the lock mechanism.Additionally, the lock mechanism of this invention operates positivelyand automatically in response to movement of the ladder sectionsrelative to each other to permit selective adjustment of the laddersections to predetermined extended positions without requiring manualmanipulation of any of the components of the lock SUMMARY OF THEINVENTION This invention relates generally to an improved extensionladder rung lock. More particularly this invention relates to anautomatically operable rung lock mechanism in which secure engagement ofaligned side-by-side rungs of movable ladder sections is insured. Stillmore particularly, this invention relates to a lock mechanism comprisinga minimum number of components including a pivotally retractable lockbody and longitudinally slidable and pivotal camming latch member foractuating the lock body during retraction or extension of two laddersections relative to each other.

This invention solves problems encountered with rung locks heretofore inthat it insures secure locking engagement of the lock mechanism withaligned side-by-side rungs of two ladder sections yet it permits easyready disengagement of the lock mechanism from one of such aligned rungsso that the ladder may be selectively and easily extended or retractedrelative to a given position automatically and without requiring anymanual manipulation of the components of the lock mechanism. Theimproved features of this invention are embodied in a mechanism having aminimum number of operative parts which are normally urged to theiroperative position by spring means effectively positioned in conjunctiontherewith.

From the foregoing it should be understood that objects of thisinvention include the provision of an improved extension ladder runglock mechanism requiring few operative components; the provision of sucha lock mechanism which is safe, efficient and automatically operable inresponse to extension or retraction of ladder sections relative to eachother; the provision of a rung lock mechanism incorporating therein apivotal lock body. and a longitudinally slidable and pivotal latchmember which operates the lock body automatically during extension orretraction of two ladder sections relative to each other; and theprovision of a rung lock mechanism which requires minimum maintenanceand which is easy to install upon conventional ladder sections.

These and other objects of this inventionwill become apparent from astudy of the following disclosure in which reference is directed to theattached drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational view of aladder showing the subject rung lock mechanism, in duplicate, inconjunction with two relatively movable ladder sections.

FIG. 2 is a side elevational view, Partly in section, taken in the planeof line 2-2 of FIG. 1 showing details of the lock mechanism.

FIG. 3 is a vertical sectional .view through the lock mechanism taken inthe plane of line 3-3 of FIG. 2.

FIGS. 4 through 6 are sequential side elevational views showing thesequence of operation of the lock mechanism when the ladder sections arebeing extended.

FIGS. 7 through 9 aresequentia1- side elevational views showing thesequence of operation of the lock mechanism when the ladder sections arebeing retracted.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIGS and 2,the lock mechanism of this invention is shown employed in conjunctionwith a'conventional extension ladder, of wood or metal, with lightweight aluminum, magnesium, or like metal being preferred for thestructural components of the ladder. In that regard, the laddercomprises two slidably interconnected sections 1 and 2, each of whichcomprises a pair of spaced parallel side rails 3 and 4,

and 5 and 6, respectively, between which extend and are secured a seriesof vertically spaced rungs. The rungs of ladder section 1 are designated7 and the rungs of ladder section 2 are designated 8.

It will be understood that ladder section 1 in the embodimentillustrated is intended to rest upon the ground or other supportingsurface with section 2 being supported by section 1 and beinglongitudinally slidable relative thereto during extension or retractionof the ladder in the manner to be described. In that regard, means foroperatively interconnecting the ladder sections, such as a series ofspaced guide brackets 9, are secured to the side rails of ladder sectionI and engage the side rails of section 2 to maintain the ladder sectionstogether during extension or retraction thereof. Other equivalent meansmay be substituted for the guide brackets 9 if preferred, in accord withprocedures well known in the ladder art.

The rung lock mechanism of this invention, generally designated 11 inFIG. 1, preferably is secured to the opposite side rails 5 and 6 of themovable ladder sections 2 for maintaining the ladder sections in anypreselected position of extension or retraction chosen in accordancewith the use to which the ladder is to be put. While a lock mechanism ofthis invention could be utilized along only one side rail of laddersection 2, duplicate lock mechanisms are preferred to provide maximumsafety. Such lock mechanisms thus act in concert with each other toperform the intended locking function.

Hereinafter reference is directed to that lock mechanism 11 which issecured to side rail 5 of ladder section 1 but it will be understoodthat the lock mechanism secured to the other side rail 6 corresponds inconstruction to the mechanism to be described.

Referring to FIGS. 2 and 3, it will be noted that the respective siderails of the ladder sections preferable are shallow channel shaped incross section in accordance with accepted ladder constructiontechniques. Desirably the rungs 7 and 8 of the ladder sections aregenerally triangular in cross-sectional configuration and include flatupper surfaces 12 and 13 on the respective rungs 7 and 8 which aregenerally coplanar to provide maximum comfort for a person standing onthe ladder when the ladder sections are oriented in a predeterminedextended position.

Secured to the base 15 of channel-shaped side rail of the movable laddersection 2 is an inverted hook-shaped mounting bracket 16. The bracket issecured in place in any suitable fashion such as by bolting, riveting orwelding. In the embodiment illustrated two or more spaced rivets 17extend through holes provided in the side rail 5 and in a flat baseportion 18 of the bracket secured in face-to-face relationship with thebase ofthe side rail 5 as best seen in FIG. 3.

Bracket 16 includes an offset shoulder portion 19 which extendsgenerally normal to the surface of the base 15 of side rail 5 and thebracket terminates in a generally vertically extending hook-shapedmounting portion 21 which extends generally parallel to the base of theside rail. Mounting portion 21 is provided with a cutout section as bestseen in H0. 2 which is contoured to conform closely with a portion ofthe periphery of a triangular rung 8 of the movable ladder section 2.The mounting bracket is secured to the movable ladder section so thatthe mounting portion of the bracket is in close contacting relationshipwith rung 8.

The mounting bracket 16 defines means for supporting the remainingcomponents of the lock mechanism in operative engagement on the movableladder section 2. Such other components include means normally extendingtransversely of the ladder side rails for simultaneously engagingaligned rungs 7 and 8 of the respective ladder sections in the form ofan elongated pivotal lock body 22, and also means for effectingselective retraction of the pivotal lock body 22 relative to suchaligned rungs so that the ladder sections may be extended or retractedselectively as will be described. This latter mentioned means comprisesan elongated movable camming latch member generally designated 23 whichis normally positioned to extend longitudinally of the ladder side railsbetween aligned rungs 7 and 8 of the ladder sections when the laddersections are positioned in a predetermined orientation.

Means for mounting the pivotal lock body and the movable camming latchon the bracket 16 comprises a headed pin 26 which extends throughmounting portion 21 of the bracket and through the lock body 22 andcamming latch 23, as best seen in FIG. 3. Opposite ends of the pin areprovided with enlarged heads 27 which prevent separation of thecomponents of the lock mechanism assembly.

Latch member 23 is generally U-shaped in cross section and is defined bya pair of generally parallel legs 28 and 29 connected by a central bightportion 31. At one end thereof, the latch is defined by a generallyhook-shaped nose portion 32 having a recess 33 thereat for the purposeto be described. At its other end the latch member is defined by arounded camming surface 33. The parallel legs of the latch member areformed with aligned elongated slots 34 therein through which pivot pin26 extends.

As best seen in FIG. 3, the latch member straddles mounting portion 21of bracket 16 and is generally longitudinally slidable relative theretodue to the pin and slot interengagement noted. The latch is also pivotalwithin limits on pin 26. intermediate its ends the latch is providedwith an exterior rounded camming surface 36 which is selectivelyengageable during operation of the lock mechanism with the respectiverungs 7 of ladder section 1.

The pivotal lock body also is generally U-shaped in cross section and isdefined by a pair of spaced legs 37 and 38 interconnected by a centralbight portion 39. Opposite ends 41 and 42 of the lock body are roundedand an opening 43 is provided through each of the legs of the lock bodycentrally of its ends to accommodate the pivot pin 26 therethrough.Between the pivot pin and the respective ends 41 and 42, the legs of thelock body are formed with generally planar aligned edges 44 and 46respectively. Such edges are adapted to engage in surface to surfacecontact with the upper flat surfaces 12 and 13 of the rungs 7 and 8 ofthe ladder section when such rungs are aligned with each other in themanner seen in FIG. 2.

As will be described hereinafter, the rounded end 41 of the lock body isadapted to be received within the recess 33 of the latch member undercertain conditions during operation of the lock mechanism as the laddersections are being extended and retracted.

Means preferably are provided for urging the lock body and the latch totheir extended positions from which positions the lock body and latchmay be selectively retracted during operation of the latch uponretraction or extension of the ladder sections relative to each other.

The means for urging the latch to its extended position comprises atorsion spring 51 coiled about a mounting pin 52 secured to the uprightmounting portion 21 of bracket 16. One end 53 of the torsion spring 5]is engaged with the shoulder portion 19 of the bracket. The other end ofthe spring is bent to extend laterally of the mounting portion 21 of thebracket and includes an end portion 54 which projects through thebracket mounting portion so as to be operatively engageable with aportion of the camming latch 23. In that regard, spring end 54 engagesan edge portion 55 of leg 28 of the latch and normally urges the latchin a clockwise direction as viewed in FIG. 2 toward its extendedposition in which it contacts rungs 7 of ladder section 1. Retraction ofthe latch relative to the mounting bracket is permitted by depressingend 54 of spring 51. Such spring end'is movable within a generallyarcuate slot 56 formed in the mounting portion 21 of the bracket as seenin FIG. 2 so that such depression may be effected.

It should be understood that when the lock mechanism is in the positionshown in FIG. 2 with the lock body 22 engaged with aligned rungs 7 and 8of the adjacent ladder sections, retraction of the ladder sectionsrelative to each other is positively precluded. However, upon upwardmovement of the movable ladder section 2 relative to the ground engagingladder section 1, retraction of the lock body and the latch may beeffected to permit further extension of the ladder or selectiveretraction thereofin the manner to be described.

in the embodiment shown, guide means preferably is provided between themounting bracket 16 and latch 23 to facilitate longitudinal slidingmovement of the latch relative to the bracket during operation of thelock mechanism. Such guide means includes a flange section 61 bent toextend generally normally relative to the plane of the mounting portion21 of the bracket as seen in FIGS. 2 and 3. Such guide flange engagesthe edge portion 55 of leg 28 of the latch along its upper extent andcooperates with the projecting end 54 of spring 51 engaged with suchedge portion of leg 28 intermediate the opposite ends of the latch tofacilitate movement of the latch.

The aforementioned means for normally urging the lock body and latchtoward their respective extended positions further includes a springmember operatively connected between the mounting bracket and the lockbody. This spring member comprises a coil spring 62 secured at one ofits ends by a mounting pin 64 to the upper end ofthe mounting portion 21of the bracket and its other end by a mounting pin 63 to the lock bodyadjacent its curved end 41. Upon counterclockwise pivotal movement, whenpermitted, of the lock body from the position shown in FIG. 2, spring 62is extended so that when pivotal forces exerted on the lock body arereleased, such spring returns the lock body to the extended positionshown in FIG. 2.

As noted previously, latch 23 straddles the mounting portion 21 ofbracket 16 and such mounting portion, as seen in FIG. 2, is providedwith a cutout section 66 adjacent its point of juncture with shoulderportion 19 of the bracket. Such cutout portion is provided toaccommodate leg 29 of the latch when the latch is pivoted in acounterclockwise direction upon engagement thereof with a rung 7 ofladder section 1 during extension or retraction of the ladder as will bedescribed.

Operation of the lock mechanism during extension of the ladder willfirst be described with respect to H65. 4 through 6, taken inconjunction with FlG. 2. When it is desired to extend the laddersections from the position shown in FIG. 2, the movable ladder section 2is drawn upwardly in any known fashion, such as by a rope and pulleymechanism (not shown) of the type commonly employed in extensionladders.

Such upward movement of ladder section 2 will draw latch 23 upwardlytherewith so that the camming surface 36 thereof is urged inwardly byrung 7 against the urging of torsion spring 54 to effect somecounterclockwise rotation of the latch about the axis of pivot pin 26.Such inward urging motion by rung 7 is accomplished when torsion springend 54 is moved within the slot 56 provided in the mounting bracket.Clearance of the latch relative to rung 7 of the fixed ladder sectionduring upward movement of ladder section 2 is shown in FIG. .5.

During such upward movement, the lock body 22 is free to pivot in acounterclockwise direction but normally the same will remain in itsextended position shown in FIGS until the same comes in contact with arung 7 of ladder section 1 which is located above the rung with which ithad previously been engaged. Upon the lock body striking such upper rung7, the lock body is pivoted in a counterclockwise direction to theposition generally shown in FIG. 6 in which position it straddles andsubstantially covers the camming latch. To permit the latch and the lockbody to pass between the generally aligned rungs as shown in FIG. 6,counterclockwise rotation of the latch and the lock body as a unit iseffected in response to the urging of the upper rung 7 against the outersurface of the lock body. Such counterclockwise rotation'is permitted byfurthertorsional movement of the end 54 of the torsion spring in slot 56as seen in FIG. 6.

It should be understood that, asladder section 2 continues to moveupwardly from the FIG. 6 position, end 41 of the lock body will clearthe upper rung 7"and,upon such clearance being effected, coil spring 62will pivot' the lock body in a clockwise direction to its extendedposition in which it lies transversely of the two rungs 7 andBLBylimiting the upward movement of ladder section 2 relative to laddersection 1 as the lock body clears rung 7, and by then allowing theladder section 2 to reverse its direction, the lock body may beengagedwith both rungs in the orientation illustrated in FIG. 2

Operation of the lock mechanism during retraction of the ladder sectionsrelative to each'other is shown in FIGS. 7

through 9. Starting with the lock mechanism in the locked position shownin FIG. 2, it is first necessary to raise movable ladder section 2upwardly relative to ladder sectionjl to bring the camming latch 23above rung 7, in the manner previously described, to the position shownin FIG. 7. Upon the camming latch reaching that position, it is merelynecessary to allow the movable ladder section to move downwardly underthe effects of gravity until the hook-shaped nose portion 32 of thelatch strikes the rung 7 with which the lock body was previouslyengaged. Upon such contact being made, rung 7 temporarily precludesdownward movement of the latch, although downward movement of laddersection 2 continues. Thus, the latch is moved longitudinally upwardlyrelative to the downwardly moving ladder section 2 with the pivot pin 26sliding within the slot 34 of the latch.

Such longitudinal sliding movement of'the latch causes the upper cammingend 33 thereof to slide along the interior of the lock body and to causethe lock body to pivot in a counterclockwise direction to the positionshown in FIG. 8. Such counterclockwise movement brings end 41 of thelock body into position within the recess 33 of the nose portion of thelatch, in which position such nose portion is oriented to clear downwardmovement of ladder section 2. It should be understood that when pivotpin 26 has reached the end of slot 34 'in the latch, continuedresistance to downward movement thereof by rung 7 will cause the latchto pivot inwardly against the urging of the torsion spring 51. Thus, thenose portion of the latch pivots inwardly in a counterclockwisedirection and carries therewith the retracted lock body. Upon suchpivotal continues, the lock body and latch will pass by rung 7 and uponthe same clearing that rung, spring 62 will urge the lock body to itsextended position and spring 51 will urge the latch the rung generallyas shown in FIG. 8 in response to continued to its extended position. Insuch positions, the components are again oriented generally as shown inFIG. 7 and are positioned to engage and clear the next lower rung in thesame fashion as just described. The sequence of selective retraction andextension of the lock body and latch is repeated until the laddersections are lowered to the position desired.

In the foregoing manner, the lock mechanism may be automatically andselectively engaged with any two aligned rungs of two extensible laddersections without requiring any manual manipulation of any components ofthe lock mechanism.

Having thus made a full disclosure'of the improved lock mechanism ofthisinvention, reference is directed to the appended claims for thescope of protection to be afforded thereto.

Iclaim: v

I. For use in an extension ladder which includes two slidablyinterconnected sections with spaced rungs on each, lock mechanismcomprising:

A. a mounting bracket to be secured to one of said ladder sectionsadjacent a predetermined rung thereon;

B. a retractable lock body pivotally mounted on said bracket adapted toengage simultaneously said rung on said one ladder section and a rung onthe other of said ladder sections when such rungs are aligned with eachother; and I C. a retractable camming latchoperatively engaged with saidlock body and mounted on said bracket for limited longitudinal andpivotal movement relative thereto;

l. said camming latch being positioned to pass between aligned rungs onsaid ladder sections during extension and retraction of said laddersections relative to each other for actuating said lock body during suchextension and retraction.

2. The lock mechanism of claiml in which said camming latch furtherincludes;

2. a recessed nose section within which a portion of said lock body isreceivable during retraction of saidrladder sections relative to eachother.

3. The lock mechanism ofclaim 2 which further includes:

D. spring means normally urging saidcamming latch to an extendedposition relative to said bracket in which position said nose section isengageable with rungs of said other ladder section and urged by suchrungs to a retracted position against the effects of said spring meansduring retraction of said laddersections'irelative to each other.

4. The lock mechanism of claim 1 which further includes:

D. spring means normally urging said lock body to an extended positionin which the same is engageable with adjjacent aligned rungs of saidladder sections.

5. The lock mechanism of claim 3 in which said camming latch furtherincludesi 3. an elongated slot extending generally longitudinallythereof, and in which said lock mechanism further includes;

E. a mounting pin extending through said bracket, said lock body andsaid slot in said camming latch, whereby said lock body may be pivotallyretracted by said camming latch in response to longitudinal slidingmovement of said latch relative to said pivot pin.

6. The lock mechanism of claim 1 which further includes:

D. spring means interposed between said bracket and said latch and saidlock body for normally urging both of the latter to their respectiveextended positions.

7. The lock mechanism of claim 6 in which said spring means includes:

l. a torsion spring mounted on said bracket and having an end thereofengaged with an edge portion of said latch normally urging said latchtowards its extended position.

8. An extension ladder including:

A. two slidable interconnected ladder sections each of which comprises:

. spaced parallel side rails, and

2. a series of spaced rungs extending between and secured to said siderails; and

B. a rung lock mechanism secured to one of said ladder sections formovement therewith during extension or retraction of said laddersections relative to each other comprising:

2. 3. a lock body pivotally mounted on said pin for movea mountingbracket secured to said one ladder section adjacent a predetermined rungof such section; a mounting pin extending through said bracket;

ment between an extended position, in which said body is oriented tosimultaneously engage said rung on said one ladder section and analigned rung on said other ladder section, and a retracted position, inwhich said lock body is oriented to pass between such aligned rungs;

a retractable camming latch mounted on said pin for limited pivotal andlongitudinal movement between an extended position, in which said latchis engageable with rungs of said other ladder section when such sectionsare bring retracted, and a retracted position, in which said latch maypass between aligned rungs of such ladder sections when such sectionsare being retracted; and

spring means normally urging said latch toward said extended position.

9. The ladder of claim 8 in which said latch includes;

a. a hook shaped nose portion having a recess therein in which an end ofsaid lock body is receivable when said lock body and said latch are intheir respective retracted positions, whereby said lock body is held outof interfering engagement with the rungs of said other ladder sectionduring retraction of said ladder sections relative to each other.

10. The ladder of claim 8 which further includes: 6. spring meansnormally urging said lock body toward its extended position.

11. The ladder of claim 8 in which said latch is generally U- shaped incross section and straddles said bracket, and in which said lock body isgenerally U-shaped in cross section and straddles said latch.

12. The ladder of claim 8 in which said spring means includes:

a. a torsion spring mounted on said bracket having an end thereofengaged with an edge portion of said latch, said spring being actuatedby said latch upon engagement thereof with a rung of said other laddersection to permit retraction of said latch so that said latch may passbetween aligned rungs of said ladder sections.

13. The ladder of claim 9 in which said latch further includes;

b. a rounded camming surface at the end thereof opposite from said hookshaped portion which is engageable with said lock body and urges suchbody toward its retracted position in response to longitudinal movementof said latch on said pin toward its retracted position in response toengagement thereof with a rung of said other ladder section.

14. The ladder of claim 11 in which said latch includes:

a. a rounded camming surface at an end thereof which is engaged with theinterior of said lock body and urges such body toward its retractedposition in response to longitudinal movement of said latch on said pintoward its retracted position in response to engagement thereof with arung of said other ladder section.

15. The ladder of claim 8 in which said latch includes a. an elongatedslot therein through which said pin extends so that said latch may movealong said pin between its extended and retracted positions.

1. For use in an extension ladder which includes two slidablyinterconnected sections with spaced rungs on each, lock mechanismcomprising: A. a mounting bracket to be secured to one of said laddersections adjacent a predetermined rung thereon; B. a retractable lockbody pivotally mounted on said bracket adapted to engage simultaneouslysaid rung on said one ladder section and a rung on the other of saidladder sections when such rungs are aligned with each other; and C. aretractable camming latch operatively engaged with said lock body andmounted on said bracket for limited longitudinal and pivotal movementrelative thereto;
 1. said camming latch being positioned to pass betweenaligned rungs on said ladder sections during extension and retraction ofsaid ladder sections relative to each other for actuating said lock bodyduring such extension and retraction.
 2. The lock mechanism of claim 1in which said camming latch further includes;
 2. a recessed nose sectionwithin which a portion of said lock body is receivaBle during retractionof said ladder sections relative to each other.
 2. a mounting pinextending through said bracket;
 2. a series of spaced rungs extendingbetween and secured to said side rails; and B. a rung lock mechanismsecured to one of said ladder sections for movement therewith duringextension or retraction of said ladder sections relative to each othercomprising:
 3. a lock body pivotally mounted on said pin for movementbetween an extended position, in which said body is oriented tosimultaneously engage said rung on said one ladder section and analigned rung on said other ladder section, and a retracted position, inwhich said lock body is oriented to pass between such aligned rungs; 3.The lock mechanism of claim 2 which further includes: D. spring meansnormally urging said camming latch to an extended position relative tosaid bracket in which position said nose section is engageable withrungs of said other ladder section and urged by such rungs to aretracted position against the effects of said spring means duringretraction of said ladder sections relative to each other.
 3. anelongated slot extending generally longitudinally thereof, and in whichsaid lock mechanism further includes; E. a mounting pin extendingthrough said bracket, said lock body and said slot in said camminglatch, whereby said lock body may be pivotally retracted by said camminglatch in response to longitudinal sliding movement of said latchrelative to said pivot pin.
 4. The lock mechanism of claim 1 whichfurther includes: D. spring means normally urging said lock body to anextended position in which the same is engageable with adjacent alignedrungs of said ladder sections.
 4. a retractable camming latch mounted onsaid pin for limited pivotal and longitudinal movement between anextended position, in which said latch is engageable with rungs of saidother ladder section when such sections are bring retracted, and aretracted position, in which said latch may pass between aligned rungsof such ladder sections when such sections are being retracted; and 5.spring means normally urging said latch toward said extended position.5. The lock mechanism of claim 3 in which said camming latch furtherincludes:
 6. The lock mechanism of claim 1 which further includes: D.spring means interposed between said bracket and said latch and saidlock body for normally urging both of the latter to their respectiveextended positions.
 7. The lock mechanism of claim 6 in which saidspring means includes:
 8. An extension ladder including: A. two slidableinterconnected ladder sections each of which comprises:
 9. The ladder ofclaim 8 in which said latch includes; a. a hook shaped nose portionhaving a recess therein in which an end of said lock body is receivablewhen said lock body and said latch are in their respective retractedpositions, whereby said lock body is held out of interfering engagementwith the rungs of said other ladder section during retraction of saidladder sections relative to each other.
 10. The ladder of claim 8 whichfurther includes:
 6. spring means normally urging said lock body towardits extended position.
 11. The ladder of claim 8 in which said latch isgenerally U-shaped in cross section and straddles said bracket, and inwhich said lock body is generally U-shaped in cross section andstraddles said latch.
 12. The ladder of claim 8 in which said springmeans includes: a. a torsion spring mounted on said bracket having anend thereof engaged with an edGe portion of said latch, said springbeing actuated by said latch upon engagement thereof with a rung of saidother ladder section to permit retraction of said latch so that saidlatch may pass between aligned rungs of said ladder sections.
 13. Theladder of claim 9 in which said latch further includes; b. a roundedcamming surface at the end thereof opposite from said hook shapedportion which is engageable with said lock body and urges such bodytoward its retracted position in response to longitudinal movement ofsaid latch on said pin toward its retracted position in response toengagement thereof with a rung of said other ladder section.
 14. Theladder of claim 11 in which said latch includes: a. a rounded cammingsurface at an end thereof which is engaged with the interior of saidlock body and urges such body toward its retracted position in responseto longitudinal movement of said latch on said pin toward its retractedposition in response to engagement thereof with a rung of said otherladder section.
 15. The ladder of claim 8 in which said latch includesa. an elongated slot therein through which said pin extends so that saidlatch may move along said pin between its extended and retractedpositions.